Fire alarm system



April 17, 1951 o. E. TENDALL FIRE ALARM SYSTEM FiledFeb. 24, 1948 Patented Apr. 17, 1951 UNITED STATES PATENT OFFICE FIRE ALARM SYSTEM` Orville Ef Tendall', Hopkins, Minn., assignor off one-'h'alf to Severlt' L. Tendall, Northfi'eld,.Minn. Apfizafibn Fbruar'y'm, 1948,. seria1" No. 10,299?

This'ihven'tion relate's't'o i'irei'a'larm''y systems for general; home'use', whether 'in' city' or country, and

which' will also' serve'` to'p'rotec't industrialv plants, business property and puhlic buildings.

Much worl'has'been' done in theifi'eld of fire alarm' systems; but it' has' resulted' in' too' much' complication and'- expense', to' he' adaptable' for' generalv` use. Fire` alarm systems' of the pneu'- matic type, heretofore constructed, have included:

a small. b'o'r'e' metallic' tube extending" in: the' form ofia'loop over' the' area tobeprotected; and con'- nectedv` with' a' device having' one` or' two' fiexible' diaphra'gm's with contacts', completing an' electric'circ'uit; resultingin` an alarm'when' pressure; due' to temperature' ris'e' air' in tube, c'au'ses' defi'ection" of diaphrag'm. These' systems' have' been' provided with' ble'e'der' vents' adj'acen't' to the'v cat'e'd' and e'x'p'e'nsii'e''co'nstruction'A in' addition' to* expeus'i've diaphragm construction. With' such delic'a'tez construction, smalltubing" is'f' necessa'rily emplyed; andl which'V is: readilyid'ented; broken or Heat ,inf sulation' has' been appliedVV to such tfubing,v to pro-VV tec't* it againstfordinary' temperature 'changes andl other fiuctuationsf not" i'ndicativeZ of fire, and to'- corrode'd and render'ed inope'ra'tive.

protect tubin'g' againstv denti'ng and bending'; Such insulationadds'-'greatly' to-the' expen's'e and to the difliculty in'- making connections;

One o'hject ofl my inventioniisto provide' a-fire alarmV system for' home and general? use', with a simplea'nd notl-expensivelfiuid pressure'responf sive device'l with considera'blel latitudei ,i still without` complioations;- sol' changesin. temperature; which ordinarily'o'ccur: or` heats' of lesser. duration* do not cause`v` alarm to be sounded, butonly conditions indica'tive' ofzfire'resultin said alarm..

Another. object ofV my inventionlis to provide a fire. alarm system.V for homeandgeneral use of pneumatic typeemployinga metallic tube of substantialborwhich is'therefore not readily rendered inoperative by denting, breaking. or' corroding, and/subjectsa considerable volume of air to heat, and. which may but need' not be loopedv over area to be protected; i

Another object of` my invention is': to. provide a fii'e alarm system for'home and' general' use",

Other objects willy be apparent from the de* scription and appended claims.

For a full disclosure'ofmyinvention, reference is` made' to the' description' following' and; to* the'` drawing; in which- Figi 1 is'a view'sh'owihg'diagrammaticall' myi` pneumatic tube fire alarm' system, with'la supply* of i chemical available' for extinguishing a'v fire'; andemploying' an electrical' alarm' device.

Fig'. 2 is a view* of a mechanical alarm device, which can be' employed vvith'the` same system:

Fig. 3 is' a view' of 'mechanism which can bef employ'ed with the same.V system, to operate' a more' powerful nie'cl'ianicall longc sounding alarm device.

Fig. 4' is a sectio'nalview; on' enlarged' scale; of a small' tube and plunger'employed' to actuate" any 'of the' different alarm' devices.

Referring now`y tov th'e'vseveralV figures of the p drawing; the reference Character' 10' indica'te's a metal tube;` extendihg' over the' area' to be" 'prot-m tec'tedl This* eidendst over' the' area' in a horilf zon'tall plane, in' a' m'an'ner shown* for" conve'ne ienc'eJ as if in'` avertical' plane' in the drawin'g This'tube is preferably" of copper;b'e'causeof'theJ i good condu'ctivit'y 'of' that metal; in* quickly trans-'f mitting heat to`the"air within the tube andcaus-d ing the air'to'expandl In protecting the average' dwelling; an arrangement of' tubin'g as shown' gen'erally in Fig. l installediin'the attic and' in the basement. will usually'suice,v as' the balance'ofV` the' 'house' ordinarilyf consists of' plastered' Walls. It is"ofcourseSe'asily'arranged'tb'suit any and all2 requirements; Whetherlarge or' small; and sev'-V eral' indep'endent systems' maybe installed' in* the same' structure, and' as" will be' later explainedi can' be adjusted to' suit varying. conditions inthe'* areas' protected by each' system; The' tube' may" be looped in cir'cuit, butwith'the'relatively'l'arge sizeoftube'employed; there' is no'd'ahg'erf of the'l tube' b'e'corning accidentally'closed, as is 'the caseA with'small'e'r tubing, which' requires'a'looped cir' cuit to insure an' alarm; The tube thereforei' pusually' has' an' e'n'dv clos'ure' I'l. The tube' may`l be s'ecured in any'convenient manner; such a`s nailed' pipe clamps; emploed by plum'be'rs" and electricians The'indic'atorend' |i2of the'tube" adjustab'lyfm'ounted'on' a" panel'v l3 by' clamps' 14". Unto" this en'dv of'the' tube and' iii' line therewith;` is mounted .a small' tube' |'-5 with'a'plmgerjl' atx tached'to a'stem' IT; This'tube` l'isprefera'bl' of precision tubing stock and of stainless steel, so there will be no corrosion. It is small in size relative to the area protecting tube. It has therefore little frictional resistance, and is responsive to a considerable extent to any increase in volume requirement of heated air in the larger tube protecting the area. The plunger IG has two leath=r cups 18, which may also consist of other types of packing. The space I 9 between these cups is filled With a grease of proper consistency, to keep the cups or packings from becoming hardened and also to lubricate walls of the tube |5. Reducing mountings and 2|, respectively, provide for transition between large tube and small tube and between small tube and plunger stem, the latter being guided in direct line motion by said mounting 2|. The mounting 2 is commonly soldered or brazed, while the mounting 2 is screw threaded to make it easy to remove and examine the plunger IB. An adjustable contact 22 is screw threadedly mounted on said stem ll. This consists of two parts as shown so as to provide thread looking action. In addition to the adjustment provided for by clamps [4 on panel 13, this contact 22 provides for further fine adjustment.

Referring now particularly to Fig. 1, which includes an electrical alarm device, and which is the most common installation, an alarm 23 and a Source of electricity 24 is provided. The alarm 23 may be a bell or buzzer and may even in some cases be a light. The source of electricity 24 may be a battery, where electric wiring is not present, but in most cases will be the usual bell transformer joined to the electric wiring. To provide a circuit and energize the alarm, a bell crank lever 25 is pivotally mounted on a panel 28. A contact 21 is provided on the panel and a contact 28 is provided on the bell crank lever. By moving the bell crank lever so that two contacts touch, a circuit is made through the pivoted mounting and the short arm of the bell crank lever. An insulation splice 29 may be provided in the long arm of the bell crank lever, to obviate any flow of electricity to or from the alarm device. With said electrical alarm, the apparatus is preferably positioned as shown in Fig. l, since the normal and out-of-contact position is assumed by gravity. It may however be made equally as operable in any other position. A stop peg 30 provides for the normal position of the bell crank lever 25; and a tension spring 3| stretched between the bell crank lever and a bracket 32, has an adjusting screw 33, by which the required tension in the spring is provided. It will be observed that the bell crank lever 25 has a relatively rather long arm, upon which the plunger stem contact 22 operates, when volume of air in system increases due to temperature increase. This added leverage is not neededfor force to operate an electrical alarm, but it provides for greater latitude of movement, relative to movement of short arm, to complete a contact. This provides for a considerable amount of free travel of the plunger, without contacts completing a circuit, resulting in an alarm. This construction therefore, can take care of fiuctuations in volume of air, due to normal temperature changes and to temporary conditions like the opening of a furnace door, and does not cause an alarm to be sounded except under fire risk conditions. The different adjustments provide for proper setting of apparatus for the particular case according to pre-determined values of volume increase. There is space adjustment 4 and spring loading adjustment. Space adjustment is accomplished by shifting indicator end of tubing backward or forward and clamping, and then supplementing by the finer screw threaded adjustment at end of plunger stem. The tension spring acting on long arm of bell crank lever, provides great range of adjustment by spring loading. By these different provisions, any required adjustment can be attained. A supply 34 of chemical, in suitable cartons or containers, is stationed on a shelf 01' convenient spot, so it may be readily available to extinguisli a fire. Any kind of chemical employed for the purpose or any kind of fire extinguisher may be used. A simple mixture, for example, generating carbon dioxide may be used. This is easily applied by throwing on in handfuls.

Referring now particularly to Fig. 2, which includes a mechanical alarm device, I provide in lieu of electrical contacts, a pair of sears 35 and 38 mounted on a panel 31. The top sear 35 is pivoted from the panel at one end, and has a stiif pivotal link 38 at the other end, connecting it to the short arm of a bell crank lever 25. An engaging notch 39 of the sears, it will be noted, is slightly off a right angle, so as to smoothen the action to disengage the sears. A spring 40 is attached to one end of the sliding sear 3G, and a connection 4| is made between the other end of the sear and a release of a mechanical alarm device. ThisV alarm device may be an alarm clock or any other spring wound i or weight operated device. It will be observed, that the other elements of the system are the same as employed for the electrical alarm device. The bell crank lever in this case, besides allowing for free travel, also makes use of mechanical advantage of the longer lever arm in disengaging the two sears. As to position, the apparatus is preferably positioned as shown in Fig. 2, since it is a natural position for the operation of the sears due to gravity. It can however be made equally as operable in any other position, by proper confinement and spring positioning of sears.

Referring now particularly to Fig. 3, which shows a heavy duty mechanical alarm device. To protect country school houses and town halls, it is necessary to actuate an alarm, which will be heard over a large area for a considerable time, in order to bring help and save the building from destruction. In school houses, where usually fires must be banked at night to last until morning, there is considerable danger of fire. Likewise in town halls, that are used only 'occasionally, there is danger of fire from stove or furnace; and with both town halls4 and school houses, there is danger of fire from grass. and forest fires and by vandals. A long distance alarm is ordinarily necessary, and if electricity is not available so a motor driven siren can be used, it must be by mechanical means. Some sirens may be operated by storage batteries, but these are not very practical to maintain in such location. A mechanical alarm requires the aid of some mechanism, to produce power by spring or by weight to operate it. A gong 42, for example, may be operated by release of a weight 43, suspended by a chain or cord 44 from a drum 45, turning a train of gears 46, which turn a cam 41, which actuates. a beater 48 on the gong 42. The release of the Weight 43 may be accomplished by a dog or latch 49, to which is attached the mechanical connection 4| of Fig, 2'; 'Ifo makeV it possible. for' the apparatusto continue the alarm for-some time, iti may' be' located in the belfry and provide for movement of the Operating, weight 43 from. there to the ground floor. If electricity is available, a powerful and far reaching motor-driven siren can of course be set in op'eration, by contacts form-- ing a circuit, as shown in Fig. 1. Besides such isolated structures as above referred to, it may be.

manner, by each being joinedeby circuit to giver indication at a central fireV fighting. source.

From; the foregoing, it will'- be' apparent. just howthe system is constructed` and. also in general' how it operates. at: atmospheric pressure, sovthere are no complications in regard to installation. By use of the several adjustments, the apparatus is readily set for the particular case according to predetermined values of volume increase. As previously referred to, there may be different areas in the same structure, that have such varying conditions, that a separate system is needed for each area. In a hot forge shop for example, conditions are different than in balance of a plant. By reoording of temperatures in the area to be protected, and making use of predetermined values of volume increase, the apparatus is set accordingly to be indicative of fire in the area. If electric, several areas may be Wired to the same alarm, or have separate alarms for each area, and the alarm may be at a distant point outside the area. The apparatus has great latituce in that it has considerable free travel range, in which the normal conditions peculiar to the particular area may be taken care of, so changes in temperature which ordinarily occur or heats of lesser duration do not cause alarm to be sounded, but only conditions indicative of fire result in such. alarm. This is made possible by the use of rather large diameter area protecting tubing and a small diameter cylinder for the signal initiating device. protecting tube is subjected to heat in case of fire, and its increased volume requirement applied to the small diameter cylinder, causes considerable movement of the plunger. This gives opportunity for adjustment, so that fluctuations from ordinary causes are well within the range of travel of the plunger when bringing about a fire alarm. Because of this, a simple system without complication can be provided. The size of the area protecting tubing may be varied with, however, the same indicator apparatus. Where a more sensitive system is required, a still larger diameter area tube may be used. It may be used to indicate other than fire conditions and cause ventilators to' be opened and other precautions taken, to prevent explosions and spontaneous combustion, such as occur in flour mills, grain elevators, coal chutes and hay barns. It may even be used to indicate Variaton in temperature conditions within large food locker and refrigeration plants. The tubing may be submerged in material like grain or slack coal, to indicate any damage or danger due to heating. It may also be used in cargos in holds of Ships, and in that and other cases, may be Thev system. is assembled A considerable volume of air in the areaV equipped withV an alarm; or. a: graph. recording;v

deviceor both. A11 in. all, thesystem issimple,

isnoteasily damaged and has substantiallatitude' vention, will be apparent to. those skilled inthe I therefore. desire to'be limitedonly by the.

art. scopei of. the appended clairns..

What I clam. is:

1. In a system. of the: charact'er described; the' combination of aclosed metal. tube of substantial bore, said. tube eXtending-over area. to be' protected, said tube being in' communication with a relatively small cylinder, aplunger with a stemin said cylinder' serving as a. signal initiatingdevice, said plungeri having a plurality'of lubri-A cated=packings and constructedso' as'l to be responsive to interior fiuid' pressure: of tube, an adjustable thrustv member on end of said stem,

a. mechanical alarm device, spring loaded compound leverage adapted to actuate said mechanical alarm device, due to sudden unusual increase of fiuid pressure in said tube, by disengaging a sliding sear from a pivoted sear by raising said pivoted sear, said sliding sear being loaded at one end by a tension spring and its opposite end having a connection to a release of said mechanical alarm device.

2. In a vsystem of the character described in claim 1, Vwith a mechanical alarm device, comprising a gong, a beater, a cam oscillating said beater, a train of gears turning said cam, a drum co-axial with the furthermost of said gears, Va weight suspended from said drum by winding its suspending member around said drum, and a release acting on said gears, all co-operating to actuate said alarm device.

3. An actuator, comprising a cylinder of relatively small diameter, a plunger in said cylinder having a plurality of lubricated packings, a stcm attached to said plunger, a cap on one end of said cylinder perforated for said stem. an adjustable thrust member screw threadedly attached to the outer end of said stem and consisting of two parts for thread looking action, a bell crank lever pivoted for engagement by said thrust member, said lever having its longer arm engaged by said thrust member and providing mechanical advantage and greater latitude of movement relative to movement of short arm, a spring positioned to provide resistance to movement of said lever by said thrust member and having means for adjusting said spring, a stop for limiting movement of said lever by said spring, means for positioning said cylinder relative to said lever subject to closer adjustment by said thrust member, and a mounting connectng said cylinder at the end opposed to its stem to an area protecting pneumatic tube of substantially greater diameter than said cylinder, whereby plunger in said cylinder is rendered sensitive to any increased volume requirement of air in said tube due to temperature increase according to size of said tube relative to said cylinder, and by varying mechanical advantage of said bell crank lever, cause different devices to be operated subject to said adjusting and positioning means to allow free travel according to pre-determined values of volume increase without causing operation of said devices.

4. An actuator, comprising a cylinder in communication with an area protecting pneumatic tube of substantially larger diameter, a plunger in said cylinder having a plurality of packings and with space for lubricating material between said packings, a stem attached to said plunger, an adjustable thrust member on end of said stem, a spring loaded bell crank lever positioned for engagement by said thrust member and to actuate different devices, and clamping means to adjustably position said plunger relative to said bell crank lever, which means together With said adjustable thrust member and said spring loading of bell crank lever provide for great latitude of adjustment to permit substantial free travel of said plunger without actuation by said thrust member within range of ordinary temperature changes or happenings in protected area, but in case of sudden unusual rise of temperature due to fire to cause said actuator to act in accordance with pre-determined values to which it has been adjusted to actuate said devices.

5. An actuator, comprising a cylinder, a

plunger with a stem in said cylinder, said plunger ,u

having a plurality of lubricated packings, an

adjustable thrust member on end of said stem, a spring loaded compound leverage arranged for engagement by said thrust member to actuate different devices and means for connecting said cylinder in communication with an area protecting pneumatic tube, said cylinder being of relatively small diameter compared to said tube. whereby sensitiveness to variations in pressure in said tube is exhibited by substantial movement in said plunger, so as to permit adjustment for free travel without actuating said devices except in cases of unusual changes of pressure indicating danger.

ORVILLE E. TENDALL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 327,324 Schuh Sept. 29, 1885 351,753 Earles Nov. 2, 1886 2,100,183 Cowan Nov. 23, 1937 2,155,345 Cowan et al. Apr. 18, 1939 2.275,949 Evans Mar. 10, 1942 

